4th International SWAT Conference 4th International SWAT Conference - - July 4 July 4 - - 6 2007 6 2007 Modelling Modelling Streamflow under Different Land Streamflow under Different Land Use Conditions with SWAT: Preliminary Use Conditions with SWAT: Preliminary Results from a Chilean Case Study Results from a Chilean Case Study A. Stehr A. Stehr , P. Debels, M. Aguayo, F. Romero, H. Alcayaga , P. Debels, M. Aguayo, F. Romero, H. Alcayaga Centre for Environmental Sciences EULA Centre for Environmental Sciences EULA - - CHILE CHILE University of University of Concepci Concepci ó ó n n , P.O. Box 160 , P.O. Box 160 - - C C Concepci Concepci ó ó n n , Chile , Chile
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4th International SWAT Conference 4th International SWAT Conference -- July 4July 4 --6 20076 2007
ModellingModelling Streamflow under Different Land Streamflow under Different Land Use Conditions with SWAT: Preliminary Use Conditions with SWAT: Preliminary
Results from a Chilean Case StudyResults from a Chilean Case Study
A. StehrA. Stehr , P. Debels, M. Aguayo, F. Romero, H. Alcayaga, P. Debels, M. Aguayo, F. Romero, H. Alcayaga
Centre for Environmental Sciences EULACentre for Environmental Sciences EULA --CHILE CHILE University of University of ConcepciConcepci óónn, P.O. Box 160, P.O. Box 160 --C C
ConcepciConcepci óónn, Chile, Chile
TOPICSTOPICS
�� Study AreaStudy Area
�� Calibration and validation 1994 Calibration and validation 1994 –– 20022002
��Model setModel set--upup
��ResultsResults
�� Validation 1975 Validation 1975 –– 20022002
�� Model Sensitivity to land use changesModel Sensitivity to land use changes
�� ConclusionsConclusions
STUDY AREA STUDY AREA
Area ~ 4265 km 2
~ 17.5% of the total Biobio Basin area
Area ~ 24500 km 2
Calibration and Validation 1994 Calibration and Validation 1994 -- 2002 2002 Meteorological and Flow DataMeteorological and Flow Data
Percentage covered by Percentage covered by each each gaginggaging stationstation
80.580.5
16.016.0
10.310.3
9.59.5
15.715.7
29.029.0
%%
MallecoMalleco
TotalTotal
RenaicoRenaico
MinincoMininco
54.254.2RehueRehue
TijeralTijeral
%%GagingGaging StationStation
Land Cover / Use & Soil TypeLand Cover / Use & Soil Type
Calibration and Validation 1994 Calibration and Validation 1994 -- 2002 2002
23.423.4Native ForestNative Forest
12.812.8Natural Natural ShrublandShrubland and Grasslandand Grassland
�� 1994 1994 –– 1999 1999 ⇒⇒⇒⇒⇒⇒⇒⇒GagingGaging station station MallecoMalleco at at CollipulliCollipulliincluded included
�� 1975 1975 –– 1982 1982 ⇒⇒⇒⇒⇒⇒⇒⇒
3 3 GagingGaging station usestation use
Model results using land use Model results using land use map from 1979 & map from 1979 &
precipitation / flow data from precipitation / flow data from 19771977--19821982
++Parameters Parameters
calibrated/validated from the calibrated/validated from the period 1994 period 1994 --20022002
Validation 1975 Validation 1975 -- 1982 1982
Nash Sutcliffe efficiency / PBIAS Nash Sutcliffe efficiency / PBIAS from the periods 1994 from the periods 1994 –– 1999 (1999 (11) ) and 1979 and 1979 –– 1982 (1982 (22))
22.5521.289.281PBIAS
EF
Index
0.800.900.901
17.1519.4710.952
0.770.740.882
MallecoMinincoTijeralP
Vergara at Tijeral
Mininco
ForestryForestry++
NativeNative
AgricultureAgriculture++
NativeNative
100% 100% ForestryForestry
100% 100% Agriculture Agriculture
Model Sensitivity to Land Use/CoverModel Sensitivity to Land Use/Cover
Scenario 1
Scenario 4
Scenario 3Scenario 2
Percentages of the different land use classes at Percentages of the different land use classes at VergaraVergara and its suband its sub --basins, for the baseline scenariobasins, for the baseline scenario
Model Sensitivity to Land Use/CoverModel Sensitivity to Land Use/Cover
Model Sensitivity to Land Use/CoverModel Sensitivity to Land Use/Cover
RehueVergara at Tijeral
Monthly hydrographs for the different land use/cover scenariosMonthly hydrographs for the different land use/cover scenariosfor a two year period (1998for a two year period (1998--1999)1999)
Model Sensitivity to Land Use/CoverModel Sensitivity to Land Use/Cover
Increasing the area covered by forestry plantations will in general produce a reduction of the mean annual flow.
Increase of the of area under agriculture will produce a increase in mean annual flows.
Mayor relative changes are expected to happen at Rehue sub-basin followed by Malleco sub-basin and Tijeral sub-basin (Rehueand Malleco are nested sub-basins of Tijeral).
The conversion of all the basin in agriculture provoke the mayorrelative changes
ConclusionsConclusions
The current model version successfully passed two validation exercises considering monthly outputs, in which 2 different land use conditions were considered (actual vs. past).
However, further research is required in order to confirm the explanatory power of the model with respect to land use impacts on basin hydrology, considering daily outputs.
The results shows in this study are an examination of the sensitivity of hydrology to a particular aspect of the ecosystem dynamics. This results only includes the response of the hydrology to changes in vegetation, to have more accurate results for plausible future scenarios changes precipitation and temperature must also be included.
However, this is a first step which provides an approach into how hydrology responds to land use change and will be valuable when analyzing relations between land use change, climate and hydrology.
AcknowledgmentsAcknowledgments
�� The present research was conducted in the framework of the The present research was conducted in the framework of the
TWINBAS (TWINBAS (Twinning European and third countries rivers basins Twinning European and third countries rivers basins
for development of integrated water resources management for development of integrated water resources management
methodsmethods) ) project, which was coproject, which was co--financed by the European financed by the European
Community through its Sixth Framework Community through its Sixth Framework ProgrammeProgramme for Research for Research
and Technological Development (Priority Area and Technological Development (Priority Area ““Global Change Global Change
and Ecosystemsand Ecosystems””; Contract N; Contract N°° 505287).505287).